<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1 {
            font-size: 35px; /* 层叠性 */
            color: red;
        }
        div {
            /* !important作用是提升优先级 */
            color: green !important; /* 继承性 */
        }
    </style>
</head>
<body>
    <div id="d1">
        <p>这是个p标签</p>
        <span>这是div内的span</span>
        <a href="">超链接</a>
    </div>
    <span>这是div外的span</span>
</body>
</html>